Concave reinforced concrete beam



Jan. 21, 1941- P ABELES 2,229,619

CONCAVE REINFORCED CONCRETE BEAM Filed June 8, 1938 Fig.7

Patented Jan. 21, 1941 2.22am concave nsmroncsn concurs mm:

Paul Abelel. Vienna. Germany Application June 8. 1938. Serial No.312,159

In Austria June 9,

lclaim.

The subject of this invention is a concave reinforced concrete beam foruse in building construction, particularly fioors.

The main object of the invention is to provide a beam of great carryingcapacity whilst having comparatively small weight. A further object isthe provision of means to fix a fiat and continuous under facing in thecase of using said beams in floors.

With these objects in view, my invention consists in using as beams forbuilding construction reinforced concave concrete being members in theform of half tubes having thin walls and produced by a centrifugalcasting process and 5 the reinforcement of which half tube is unevenlydistributed over its cross sectional area in accordance with the staticrequirements.

The beam is flattened on one side for the pur means (without theintermediate layers of con-u crete necessary heretofore).

The use of concave beams is very satisfactory and results in anincreasing of the carrying capacity as compared to the flat beams owingto the action as a spatial or arched construction. Such a mode ofactionhas not been achieved a with the known concave beams produced otherwisethan by centrifugal casting process, as it was not possible to attainhalf tubes having sufficiently thin walls; However the production of 35two half tubes having small thickness can be effected simultaneously ina very simple manner by the centrifugal casting process, so that thementioned difilculty with regard to production as compared with theknown construction of o fioor beams no longer obtains. The improvementsin the quality of the concrete dueto centerifugal moulding enables thewalls to be made considerably thinner than was heretofore possible sothat the transport and the laying of the finished concrete beams isfacilitated, and on the other hand there is a substantial improvementfrom an economic point of view. There is also a considerable saving ascompared with the usual half tubes which are not produced by cen- 50trifugal moulding, because owing to the greater strength ofcentrifugally moulded concrete load relieving stresses are developed inthe tensile reinforcement and this sheet may be amplified by connectingall the reinforcement elements to ll form a rigid framing, the auxiliarylongitudinal PATENT OFFICE REiSSUED Nov 28 1944 and transversereinforcement as stirrups or stirrups and tension anchorage members. orspiral members, resulting in this case in relieving stresses beingdeveloped.

Practical embodiments of the invention are shown in the accompanyingdrawing on which like references indicate corresponding parts.

Fig. 1 is a cross section of a floor comprising concave beams inaccordance with my invention;

Fig-2 is a section of means for the production m of two half tubessimultaneously:

Figs. 3 and 4 are sections of modified forms of the beam;

Fig. 51s a side elevation of a beam Figs. 6 and 'l are cross sections onthe lines VI--VI and VII--VlI respectively of the beam shown in Fig. 5;

Fig. 8 is a cross section of a modified form of the beam and Figs. 9 to13 are cross sections of the beam showing different means for fixing aflat under facing.

The floor shown in Fig. 1 consists of a row of concave beams I producedby centrifugal moulding. These beams present a semi-circular cavity la;the reinforcement 2 is provided in their tension zone. The beams mayhave lateral pro- Jections 3. The hollow beams l arranged side by sideare joined togetherby filling in the joints with cement mortar or meagreconcrete 4. so that the adjoining hollow beams are interconnected anduniform deflection is ensured. Floor filling I over the beams isprovided in the usual manner. Joists 8 with floor boards I above arearranged in the well known manner in connection with such floorings inthe recesses between the individual beams, and the result is acomparatively low floor structure whilst utilizing to the full theheight of the hollow beams. The beams, may be spaced and the spacingsmay be bridged by filling members or slabs resting on the lateralprojections 3. In this case the joints 4 are dispensed with.

The floor filling i also may be dispensed with in which case the floorboards I rest directly on o the beams or are disposed in another knownmanner.

For the producing ofthe beams it is useful to add substances to theconcrete mortar, which 50 reduce the specific gravity, as natural lightmateriais especially volcanic ones, fragments of bricks, pumice-stone orothers.

Fig. 2 shows the method of producing such hollow beams I withprojections 3 by centrifu- 5 Id moulding. Plates I are laid in the wellknown manner in the mould I in order to separate the casting into twohollow beams. In view of the fact that in centrifugal moulding theforces act radially outwards and not in the direction of rotation. thiscentrifugal moulding results in the concrete being Just as dense in theprojections I as in the other parts. It is: possible in a simple manner.to put in the reinforcement members and keep the same in a stretchedstate during the centrifugal casting process.

From the point of view of economy it is desirable to employ a mouldwhich will produce two half tubes the width of which is greater than theheight (Fig. 2) or a somewhat flattened arch, because the amount ofconcrete per square metre of flooring will be less than in the case ofthe known structures of greater height. To enable such hollow beams tobe produced by a centrifugal moulding process counterwelghts II areattached to the ring ill of the mould 2 to balance the mass. Theprojections 2 are slightly bevelled laterally to facilitate the removalof the two halves of the mould 8.

Figs. 3 and 4 show different cross sections and different reinforcement.The beam shown in Fig. 3 is multi lateral externally. In addition to thetension reinforcement members 2 there are also transverse reinforcementmembers l2 and auxiliary or secondary reinforcement members II whichtogether form a rigid frame work and relieve the stresses in the tensionzone 2. The transverse reinforcement i2 may consist of stirrup or spiralmembers. The beam shown in Fig. 4 is semi-cylindrical and only flattenedat the top at the part subjected to compression. In this case there areprovided only stirrup members it as transverse reinforcement.

Having regard to the particular denseness produced by centrifugalmoulding and the increase in the strength it is possible to entirelydispense with the transverse connection and auxiliary longitudinalreinforcement and to only provide the statically necessary tensionreinforcement 2. In This case no relieving stresses are developed indefault of the auxiliary reinforcement but the strength of the concreteis increased because, as proved by tests, concrete produced bycentrifugal moulding but devoid of reinforcement is stronger than thatprovided with a weak reinforcement framework. The otherwise requiredstirrup members to withstand the thrust stresses are not required,providing that there are no particularly heavy loads and wide spans,since the concrete members alone are capable of taking the thruststresses. It is, therefore, only necessary to provide several stirrupmembers for the purpose of the mounting and to reduce the transversereinforcement to the minimum required for effecting the bond. Such astructure is shown in Figs. 5 to 7. In addition to the tensionreinforcement 2, which does not project beyond the end of the hollowbeam, tension reinforcement members 2' are provided in the usual mannerat the upper andenablingaconnectiontobemadegratingorcrossbeamsatthepointoffixing with complete or partial fixingin. The reinforce- 5 meat members 2 and 2' are connected by stirrupmembers ll of which there are only as many as are required to hold theframework together when placing it in the mould. In addition, there maybe separate stirrup members ll of a number suillcient to ensure thebond. Fig. 7 also shows how the reinforcement 2 is held in position inthe well known manner by concrete rings l1.

-Asshownin1"ig.8,irontiemembers "maybe provided which on the one handserve to further secure the longitudinal reinforcement members, and onthe other hand serve also as tension anchorage members. Such hollowbeams with tension anchorage members It are suitably arrangedintheendpartsofthefioors. Thetensionanchorage members may also serve tofix the flat under facing. To close the hollow beams to gratings andcross beams suitable pre-cast concreteplates|l(1"igs.5and6)areused. Buchplatesmayalsobeprovidedintherecesses which are formed by the top of eachtwo adjacent As shown in Fig. 9, a flat and continuous under facing isattained by bricks II, which are fixed to the lower face of the beam I,these spaces between said bricks II are bridged by additionalbrick-slabs 22. The bricks II are provided with ribs 2| on their topface. Said bricks are placed in position in the centrifugal mould (Fig.2) prior to the charging of the latter with concrete mortar so that thebricks adhere to the lower face of.

the beam after hardening of the mass.

Fig. 10 shows a beam, in the lower face of which cross-rods 22 arecounter-sunk to bridge the cavity of the beam and enabling to fix a fiatunder facing onto the beam. For the same purpose. laths 22 may becountersunk lengthwise in the lower face of the beam as shown in Fig.11.

For fixing a fiat under facing, wire or flat-iron hooks may be employed,which project on the lower face of the beams. As shown in Fig. 12, saidhooks 24 are formed as a continuation of the stirrups l4, wound roundthe bars 2. During the centrifugal casting process said continuations24' are laterally bent off being held fast between the two halves of themould I (Fig. 2). Fig. 13 shows a modified form in which separate hooks2| are fixed to the reinforcement bars 2.

I claim:

A concave reinforced concrete beam comprising a centrifugally cast halftube, that part of said beam which is required to endure tensile stressbeing flattened to permit said beam to be used as an independentsupporting beam for ceilings, bricks fixed to the lower face of saidhalf tube, the space between said bricks being bridged by additionalbrick slabs.

PAUL ABELES.

